Re: [PATCH] mm, page_alloc: fix the duplicate save/ressave irq

[Vlastimil Babka <vbabka@suse.cz>]

On 03/13/2017 09:02 AM, zhongjiang wrote:
> From: zhong jiang <zhongjiang@huawei.com>
> 
> when commit 374ad05ab64d ("mm, page_alloc: only use per-cpu allocator for irq-safe requests")
> introduced to the mainline, free_pcppages_bulk irq_save/resave to protect
> the IRQ context. but drain_pages_zone fails to clear away the irq. because
> preempt_disable have take effect. so it safely remove the code.
> 
> Fixes: 374ad05ab64d ("mm, page_alloc: only use per-cpu allocator for irq-safe requests")
> Signed-off-by: zhong jiang <zhongjiang@huawei.com>
> ---
>  mm/page_alloc.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 05c3956..7b16095 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2294,11 +2294,9 @@ void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp)
>   */
>  static void drain_pages_zone(unsigned int cpu, struct zone *zone)
>  {
> -	unsigned long flags;
>  	struct per_cpu_pageset *pset;
>  	struct per_cpu_pages *pcp;
>  
> -	local_irq_save(flags);
>  	pset = per_cpu_ptr(zone->pageset, cpu);

NAK. we have to make sure that pset corresponds to the cpu we are
running on.

>  
>  	pcp = &pset->pcp;
> @@ -2306,7 +2304,6 @@ static void drain_pages_zone(unsigned int cpu, struct zone *zone)
>  		free_pcppages_bulk(zone, pcp->count, pcp);
>  		pcp->count = 0;
>  	}
> -	local_irq_restore(flags);
>  }
>  
>  /*
> 

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